遥远的OH/IR星V1648 Aql（IRAS 19386+0155）的光谱
Optical spectrum of distant OH/IR star V1648 Aql (IRAS 19386+0155)
摘要：
在6米望远镜上获得了恒星V1648 Aql（=IRAS 19386+0155）的光谱，光谱分辨率为R $\ge$ 60000。从许多金属碎片上测得的日心径向速度等于V $_r$ = $10.18\pm0.05$ km s $^{-1}$（V $_{\rm LSR}$ =18.1 km s $^{-1}$）。我们分别在VPDMATHABMN =9.2、$-3.4$和$-12.8$ km s $^{-1}$处测定了NaI D~线剖面中的大气、星周和星际分量。20个DIBs的平均速度V $_r$（DIBs）= $-12.5\pm0.2$ km~s $^{-1}$与星际NaI分量一致。在光谱中检测到强度约为局部连续谱水平10%的弱发射，它们被识别为低激发金属线。它们的平均位置，V $_r$ = $8.44\pm0.28$ km s $^{-1}$，可能表明在恒星大气层的上层存在一个弱的速度梯度。根据光谱数据并考虑到星际和星周红化，我们估算了恒星的光度M $_V\approx-5^{\rm m}$，同时也得到了距离d $\ge1.8$ kpc的较低估计。利用模型大气方法，我们确定了V1648 Aql的基本参数和大气化学丰度，证实了它是一颗后AGB星。
英文摘要：
An optical spectrum of the star V1648 Aql (=IRAS 19386+0155) was obtained at the 6-meter telescope with a spectral resolution of R$\ge$60\,000. Heliocentric radial velocity measured from numerous metallic absorptions is equal to V$_r$=$10.18\pm0.05$ km s$^{-1}$ (V$_{\rm LSR}$=18.1 km s$^{-1}$). We determined the atmospheric, circumstellar, and interstellar components in the profile of the NaI D~lines at V$_r$=9.2, $-3.4$, and $-12.8$ km s$^{-1}$ respectively. The averaged over twenty identified DIBs velocity V$_r$(DIBs)=$-12.5\pm0.2$ km~s$^{-1}$ coincides with the interstellar NaI component. Weak emissions with an intensity of about 10% of the local continuum level were detected in the spectrum; they are identified as low-excitation metal lines. Their averaged position, V$_r$=$8.44\pm0.28$ km s$^{-1}$, may point to the presence of a weak velocity gradient in the upper layers of the stellar atmosphere. Based on the spectroscopic data and taking into account the interstellar and circumstellar reddening, we estimated the star's luminosity M$_V\approx-5^{\rm m}$ and also obtained the lower estimate of distance d$\ge1.8$ kpc. Using the model atmosphere method, we determined the fundamental parameters and chemical abundances in the atmosphere approving the status of a post-AGB star for V1648 Aql.
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